FIG. 4 is a block circuit diagram schematically showing a conventional wireless video system. A conventional wireless video system 140 in FIG. 4 is composed of a wireless video transmitting device 141 and a wireless video receiving device 142. The wireless video transmitting device 141 is composed of a wireless video transmitter 153 and an antenna 154. The wireless video receiving device 142 is composed of an antenna 155 and a wireless video receiver 156.
A video tape recorder (VTR) 152, etc., for example, is connected to an input side of the wireless video transmitter 153, whereas the antenna 154 is connected to an output side of the wireless video transmitter 153. Further, the antenna 155 is connected to an input side of the wireless video receiver 156, whereas a personal computer (PC) 157 and a monitor 158, for example, are connected to an output side of the wireless video receiver 156.
Next, operation of the conventional wireless video system 140 in FIG. 4 will be explained. On a wireless video transmitter 153 side, a video signal P and an audio signal S that are outputted from the video tape recorder (VTR) 152 are converted into a high-frequency signal RF by the wireless video transmitter 153, and the high-frequency signal RF is then transmitted to the wireless video receiver 156 via the antenna 154.
On a wireless video receiver 156 side, the high-frequency signal RF that is transmitted from the wireless video transmitter 153 is received at the antenna 155. The received high-frequency signal RF is converted back into the original video signal P and the audio signal S by the wireless video receiver 156. The video signal P and the audio signal S are supplied to an AV input terminal of the personal computer (PC), and are displayed on the monitor 158.
As described above, by employing the wireless video system 140, it is possible to view a video picture and hear sound of the video tape recorder (VTR) 152, etc., for example, on the personal computer (PC) 157, etc., for example, which is remotely located from the video tape recorder (VTR) 152, etc. Further, by connecting an outdoor antenna to the video tape recorder (VTR) 152 and selecting television broadcasting on the video tape recorder (VTR) 152 so that the video tape recorder (VTR) 152 outputs the video signal P and the audio signal S of the selected television broadcasting, it is possible to view the television broadcasting on the personal computer (PC) 157 even at an indoor place where the reception of a television signal is not good.
Further, in order to transmit the video signal P and the audio signal S from the wireless video transmitter 153 to the wireless video receiver 156 as the high-frequency signal RF, a spread spectrum technique is used for 2.4 GHz, for example, of a frequency band of the high-frequency signal RF. A general communication method employing the spread spectrum technique is as follows. On a transmitting side, an input baseband signal such as the video signal P and the audio signal S is modulated, and subjected to the spread spectrum using a spread code, so as to be transmitted as the high-frequency signal RF. The spread spectrum signal that is received on a receiving side is demodulated (reverse spread spectrum) into the original signal such as the video signal P and the audio signal S, using the same spread code as the spread code on the transmitting side. Further, when wireless LAN is used on the personal computer, the same spread spectrum technique is used for the 2.4 GHz band.
However, in the conventional technique, for displaying the video signal P and the audio signal S on the personal computer, the analog video signal has to be converted back into the digital video signal at the personal computer, thereby enlarging a processing circuit on a personal computer side.
Further, wireless signals may be mutually interfered when the wireless LAN and the wireless video receiver are simultaneously used on the personal computer.
Further, when respective circuits that are commonly used for the wireless LAN and for the wireless video receiver are provided on a printed board in a small size, in order to use the wireless receiving device both as the wireless LAN receiver and the wireless video receiver, the mutual interference of the signals between the respective circuits, the entrance of a signal of a circuit into the other circuit, etc. cause the signal loss and error rate deterioration of communication signals. This causes a problem in which a video picture, sound, and wireless LAN data cannot be transmitted and received in a good condition.